The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Fuel injectors are used to directly inject pressurized fuel into combustion chambers of internal combustion engines. Known fuel injectors include electromagnetically-activated solenoid devices that overcome mechanical springs to open a valve located at a tip of the injector to permit fuel flow therethrough. Injector driver circuits control flow of electric current to the electromagnetically-activated solenoid devices to open and close the injectors. Injector driver circuits may operate in a peak-and-hold control configuration or a saturated switch configuration.
Fuel injectors are calibrated, with a calibration including an injector activation signal including an injector open-time, or injection duration, and a corresponding metered or delivered injected fuel mass operating at a predetermined or known fuel pressure. Injector operation may be characterized in terms of injected fuel mass per fuel injection event in relation to injection duration. Injector characterization includes metered fuel flow over a range between high flowrate associated with high-speed, high-load engine operation and low flowrate associated with engine idle conditions. Advanced engine operations, such as homogeneous-charge compression ignition (HCCI) and spray-guided-stratified-charge engines, sometimes utilize a plurality of fuel injection events in rapid succession, each including an injected fuel mass relatively small in magnitude.
It is known for engine controls to benefit from injecting a plurality of small injected fuel masses in rapid succession. Generally, when a dwell time between consecutive injection events is less than a dwell time threshold, injected fuel masses of subsequent fuel injection events often result in a larger delivered magnitude than what is desired even through equal injection durations are utilized. This undesirable occurrence is attributed to the existence of a residual magnetic field produced by the preceding fuel injection event that offers some assistance to the immediately subsequent fuel injection event. It is known to compensate for the effect of the larger than desired delivered magnitude of injected fuel mass by adjusting the injection duration of the subsequent injection event; however, the corresponding subsequent fuel injection can become unstable resulting in unacceptable repeatability.